The present invention relates to a method and apparatus for guiding diagnostic and therapeutic devices into tortuous body passages, such as may be found in the urologic, cardiovascular, gastrointestinal and pulmonary systems. In its more specific aspects, the invention is concerned with a system which employs a guide wire to guide the instrument into place and an improved guide for traversal over the wire to direct an instrument to the desired location.
In the prior art, it has been common to place instruments within body passages by passing the instruments over a previously placed guide wire. This technique ensures that the instrument will follow the correct pathway and helps minimize trauma associated with instrument advancement. Guidance is normally accomplished by threading the previously placed guide wire through a lumen which runs the entire length of the instrument. This lumen, typically called a "through-lumen", can serve other functions besides guide wire accommodation, such as: fluid infusion, pressure monitoring, or the passage of other instruments for visualization and therapy.
An example of a prior art system where an instrument is advanced over a previously placed guide wire may be seen in U.S. Pat. No. 4,526,175. In the device of that patent, a through-lumen runs the full length of the instrument to accommodate a guide wire. It is also known in the prior art to provide an instrument carrier wherein a preformed catheter is placed in advance of the instrument, much as a guide wire would be placed, and then the instrument is passed through the catheter to position the instrument within a body passage. Such a system may be seen in U.S. Pat. No. 4,195,637.